1. Field of the Invention
The present invention relates to the recording of information on magnetic tapes and particularly to prevention of the accidental erasure of magnetic tapes. More specifically, this invention is directed to apparatus which cooperates with a self-contained magnetic tape cartridge to prevent the recording of information on a magnetic tape having stored thereon pre-recorded information which is to be retained. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in tape recorders of the type which receive a tape cartridge or cassette and wherein playback may be effected in either direction of travel of the tape.
Commercially available tape cartridges are provided with means which cooperate with sensing and control apparatus on the tape recoder for preventing the inadvertent erasure of signals previously recorded on the magnetic tape. Such erasure prevention means will typically comprise a pair of detachable tongues or tabs disposed adjacent the ends of the edge of the cartridge positioned opposite to the edge through which the tape is presented to the playback or recording head. In order to prevent inadvertent erasure of information on the tape, or on one track of the tape, the tabs or appropriate tab is removed from the cartridge. Thereafter, when the cartridge with the tab removed is introduced into the tape recoder, apparatus on the recorder detects the absence of the tab and commands a control mode which prevents recording. In this manner recording on the track associated with the removed cartridge tab, which would result in the erasure of the previously recorded information, is prevented. When the cartridge is turned over to thereby permit use of the second track, the presence or absence of the tab on the opposite end of the cartridge will be sensed and recording on the second track will be prevented or enabled as appropriate.
In the interest of avoiding the necessity of removing and turning over the cartridge after the magnetic tape has been completely transferred from a first to a second or take-up reel within the cartridge, the transfer having occurred during playback of or recording on a first track, it has been proposed to provide tape recoders with the capability of allowing the tape to run in either direction at normal speed thus permitting utilization of a second track when the tape drive is reversed. This arrangement permits playback or recording on a first track with the tape moving in a first direction and, after the tape has been completely transferred, the playback or recording may be continued on a second track as the tape moves in the opposite direction. The tape recorder will normally also be able to rapidly rewind the tape in either direction without playback or recording.
As used herein it is to be understood that the term "track" refers to that portion of the magnetic recording medium which is employed in each direction of movement of the tape. Thus, the term track encompasses a plurality of channels which are recorded or replayed simultaneously as is common in stereophonic equipment.
As previously noted, in conventional tape recorders which provide for the turning over of the cartridge in order to permit utilization of both tracks, the reversal of the cartridge presents the tab or other indicating portion of the tape cartridge to a detecting or sensing mechanism in the recorder. The sensing mechanism controls whether recording will be permitted on the track to be presented to the recording-playback head. On tape recorders which have the capability of transferring the tape in either direction at the normal or playback speed, there is presently no apparatus available which for both directions of travel, provides a signal which indicates whether recording is to be prevented or permitted. The presently available detecting devices, as used on recorders which require reversal of the cartridge, are not suitable for use on such reversible recording apparatus since the detecting devices can perform their required control function in only one direction of movement of the tape. Thus, the presently available apparatus will continue, in accordance with the signal provided for the first direction of tape movement, to enable or prevent the recording for the second direction of movement. Obviously, this manner of operation could result in an undesired erasing of the tape track corresponding to the second direction of tape transfer or unwanted prevention of recording during the second direction of tape movement.
It has been proposed to provide for the simultaneous detection of the state of the tab or other indicia providing device at the two ends of the cartridge and to prevent recording when a signal commensurate with a desire to retain recorded information is detected at either of the opposite ends of the cartridge. While this would eliminate the risk of inadvertent erasure, it would also substantially reduce the flexibility of the recording apparatus by reducing the complete utilization of the recording possibilities.